1. FIELD OF THE INVENTION
This invention pertains to the field of working or contouring planar structures. Further, this invention relates to a method of contouring board structures composed of a porous plastic layer sandwiched between opposing paper surfaces. Additionally, this invention pertains to methods of preparing plastic laminate structures for contouring to predetermined radii of curvature.
2. PRIOR ART
Structural boards having a foamed plastic layer sandwiched between paper layers are well known in the art. However, such prior structural boards are formed in planar elements and cannot be contoured. When such boards are bent they generally are found to break. Further, even when a small bend is made in such board elements, it has generally been found that when pressure is released from the board it has a tendency of reforming itself into a planar member. Thus such board members cannot be used in the manufacture of a wide variety of articles which require light weight combined with structural integrity but also necessitate contours having differing radii of curvature.
In my copending application Ser. No. 462,397, filed Apr. 19, 1974, I have taught the method of producing airplane wings from a planar laminate structure of the type herein described. By perturbing the method as therein described I have now discovered a general method of working the laminate material to produce a structure useful in building a wide variety of objects such as lampshades, canoes, etc.